I used one of their product setups on a '70 Lemans/GTO I had years ago...
it greatly improved handling....
nowever the tires reasonably available for the times were limiting...245/60/15 is about it....255? in rear....
I did know when I was doing my '72 vette some 15 years ago, but just could not justify the outlay for any 'improvment' being so marginal compared to my other changes....
I didn`t think Global sold the bushings separately any more....you might want to call and check (ask for Doug).
Edit: found my instruction sheet, mine are from GW.